&NA;One hundred seventy‐eight patients with cancer of different segments of the colon were treated with preoperative radiation and surgery. Preoperative radiation with 25 MeV betatron was employed according to the method developed by the authors. Radiation treatment was tolerated by patients in the absence of manifest general and local reactions. No decrease below 3000 in the rate of leukocytes was observed after a total dose of up to 40 Gy. After radiotherapy, improvement in the general state was achieved in 72 percent and positive roentgenologic findings were seen in 70.8 percent of patients. The preoperative irradiation therapy was followed by 153 radical and 28 palliative operations. There was no increase in postoperative morbidity or mortality. The morphologic study of surgical specimens showed that considerable changes in the tumoral tissue, including disappearance of cancer cells, were seen in 75 percent of cases. The five‐year survival rate of 112 patients after radical surgery indicates that it is worthwhile to use the combined treatment approach for tumors located in the right colon and in cases of suspected or existing infiltration into adjacent organs and tissues.